TM 1-1520-240-MTF4-58c. Perform GPS system Start-Up procedure.Ensure four (4) satellite measurements(SAT) are being used and estimatedposition error (EPE) is 50 (meters) or lesswith keys loaded or 200 (meter) or less witha cold start.d. Fly helicopter over surveyed test courseconsisting of two (2) waypoints used ascheckpoints (CP) a minimum of 20KMapart.e. To minimize errors in establishing positionsover the checkpoints (CP), the altitude shallbe the lowest compatible with safetystandards.f. If checkpoint (CP) information was notentered through the data loader duringStart-Up, with the Mode switch set to NAVenter checkpoints using the CDU.g. Set Mode switch to NAV.h. Depress GPS/DOP select button on HSIMode Select Panel.i. Set Data switch to MSN. Depress waypointkey (WP) until > is displayed in upper leftcorner of display (meaning destinationmode). On Page 1, ensure that an arrow (²)is in front of Doppler Only (DOP ONLY) andGPS Only (GPS ONLY), on lines 3 and 4respectively.j. Set the Data switch to OPT.(1) Select the Doppler backup mode onPage 1, Line 1 (* Back-Up displayed).(2) Slew (µ) down to Page 3.